Catalase regulates the endogenous peroxide of ocular humors at physiology levels, and protects superoxide dismutase of lens from the inhibitory effect of H2O2 in vitro and in vivo. Superoxide dismutase of eye, in turn, protects the lens from deleterious effects of superoxide anion radical (O2.-). Impairment of the enzymic defenses against H2O2 or O2.- might result in the production of a highly damaging oxidant, the hydroxyl radical. Since H2O2 or its equivalent free radicals are suspected in cataractogenesis, the proposed studies are aimed to explore the relative functions of catalase and superoxide dismutase in lens and eye tissues in protecting the lens from these agents, and to investigate the role of the oxygen derivatives in cataractogenesis. Studies will be conducted to generate and estimate O2- and OH. in vitro using lens culture or homogenate. Since we observed in 3-aminotriazole cataract that membrane permeability is deranged, we shall investigate the possibility of membrane damage caused by H2O2 and O2.- by oxidation of -SH of transport protein and peroxidation of membrane lipids. To observe oxidative damage to membrane transport of lens, we shall examine cation transport, mediated transport of sugars, amino acid transport and simple diffusion using appropriate radioactive probes. We shall incubate lenticular plasma membranes in the presence of H202, O2-, or OH generated enzymically and measure malonaldehyde produced as an index of oxidative damage to membrane lipids. Incorporation of 3H-L-leucine into lens protein will be observed to assess protein synthesis in cataract. In cataract, energy production will be evaluated by observing 32Pi incorporation into ATP, and energy utilizaton by assaying Na ion, K ion-ATPase of lens. Since our overall objective is to investigate cataractogenesis in the human and determine preventive therapy, we shall study some of the above-mentioned parameters using normal and cataractous lenses of the human. Finally, we will try to reverse or arrest the early cataract in rabbit by administering free radical scavengers.